A novel method to improve fatigue behaviors of holed structures based on electromagnetic force

In this study, a novel method stress wave strengthening (SWS) process based on electromagnetic force was proposed to improve the fatigue life of holed structures. Corresponding tests were carried out to explore the fatigue performance of SWS. Cold expansion (CE) was also investigated for comparison. The fatigue life of SWS and CE samples were evaluated, moreover, the mechanisms of fatigue failures and life enhancements were also discussed. Results showed that double-side SWS extended fatigue life significantly and reduced stiffness degradation more effectively with respect to CE process. Moreover, fatigue cracks commonly appeared at mid-planes of hole surfaces and horizontally grew in SWS samples, which differed a lot from CE samples. Through the residual stress measurement, it is seen that more uniform residual stress along axial direction can be obtained by SWS compared to CE, which can explain the fatigue life enhancement and failure mechanism of SWS method.

Understanding the Relations between Surface Stress State and Microstructure Feature for Enhancing the Fatigue Performance of TC6 Titanium Alloy

Fatigue performance has always been an important factor affecting the application of titanium alloy. The service life of TC6 titanium alloy is easily reduced under a continuously alternating load. Therefore, there is an urgent need for a new method to improve fatigue performance. Laser shock peening (LSP) is a widely proposed method to enhance the fatigue performance. Here, through experiments and finite element simulations, it was found that LSP can prolong the fatigue life of TC6 by improving the surface stress state. In strengthening processes, the generation of residual stress was mainly attributed to the change of microstructure, which could be reflected by the statistical results of grain sizes. The content of grains with a size under 0.8 μm reached 78%, and the microhardness value of treated TC6 was 18.7% higher than that of an untreated sample. In addition, the surface residual compressive stress was increased to −600 MPa at the depth of 1500 μm from the surface. On this basis, the fatigue life was prolonged to 135%, and the ultimate fracture macroscopic was also changed. With the treatment of LSP, the fatigue performance of TC6 is highly promoted. The strengthening mechanism of LSP was established with the aim of revealing the relationship between microstructure and stress state for enhancing the fatigue performance in whatever shapes.

POS0634 DO BIOLOGICS IMPROVE FATIGUE IN PATIENTS WITH RHEUMATOID ARTHRITIS?

Background:Fatigue is a significant issue in rheumatoid arthritis (RA) with no accepted evidence-based management guidelines. Several studies suggested that biologic Disease Modifying Anti-Rheumatic Drugs (bDMARDs) have a direct role on fatigue in RA.Objectives:This study aimed to compare fatigue between patients treated with bDMARDs and conventional synthetic Disease Modifying Anti-Rheumatic Drugs (cs DMARDs).Methods:We conducted a longitudinal study including patients with RA (ACR/EULAR 2010). Patients with other acute or chronic diseases that may induce fatigue (such as cancer, infection or depression) were excluded. Demographic data and the following disease-related parameters were collected: pain Visual Analog Scale (VAS), Global Patient Assessment (GPA), tender joint count (TJC), swollen joint count (SJC), Erythrocyte Sedimentation Rate (ESR), C Protein Reactive (CRP), Disease Activity Score 28 (DAS28), Health Assessment Questionnaire (HAQ) and DMARDs used. Fatigue was assessed at baseline (T0), at 6 months (T6) and at 12months (T12) using the Functional Assessment of Chronic Illness Therapy – Fatigue (FACIT-F) which is a short 13-item questionnaire validated in RA. The score FACIT-F ranges between 0 and 52. Fatigue was considered mild if the FACIT-F score was ≥40, moderate if 20≤FACIT-F<40 and severe if 0≤FACIT-F<20. A p value inferior to 0.05 was considered significant.Results:We included 100 RA patients (84 women and 16 men) with a mean age of 49.5±10 years old [18-65]. The mean disease duration was 87.3 months [1-360]. The mean pain VAS was 49 cm [0-100] and the mean GPA was 47.8 cm [0-100]. The mean TJC and SJC were 5.3 [0-36] and 1 [0-9] respectively. The mean levels of ESR and CRP were 38.1 mm [10-120] and 10.8 mg/l [2-61] respectively. The mean DAS28 ESR was 3.68 [1.90-8.33] and the mean HAQ score was 0.90 [0-2.75].Eighty-three percent of patients used csDMARDs: Methotrexate (n=96), sulphasalazine (n=28), leflunomide (n=21), and hydroxychloroquine (n=12). bDMARDs were prescribed in 17% of patients: Rituximab (n=10), Infliximab (n=9), and Etanercept (n=5).At baseline, the mean FACIT-F score was 27.1 [0-51]. Moderate fatigue was noted in 57% of cases and severe fatigue in 26% of cases. Patients on csDMARDs had a lower FACIT-F score when compared to patients on bDMARDs (26.89 versus 28.41), but the difference was not statistically significant (p=0.630).The mean FACIT-F score was 27.41 in bDMARDs patients versus 29.80 in csDMARDs patients (p=0.497) at T6, and 32.35 versus 33.65 respectively at T12 (p=0.695).The mean delta FACIT-F was 2.18 in bDMARDs patiens versus 2.73 in csDMARDs patients between T6 and T0 (p=0.815), and 3.94 versus 7.2 respectively between T12 and T0 (p=0.807).When considering all patients, a significant positive correlation was noted between delta FACIT-F and delta DAS28 at T6 (r=0.418, p<0.001) and at T12 (r=0.338, p<0.001).Conclusion:RA patients treated with bDMARDs didn’t show significant improvement of fatigue in comparison with those treated with csDMARDs. Further studies are needed to determine if biologics improve fatigue, and whether the improvement results from a direct action on fatigue or indirectly through reduction in disease activity.Disclosure of Interests:None declared

Fatigue in CKD

Fatigue is a commonly reported and debilitating symptom among patients with CKD, yet little is known about its epidemiology, pathogenesis, and treatment. Various measurement tools have been used in published studies to identify and quantify fatigue. These include several single-item measures embedded in longer questionnaires for assessing depression, quality of life, or symptom burden in patients with kidney disease. Approximately 70% of patients with CKD report fatigue, with up to 25% reporting severe symptoms. Patient-reported fatigue is associated with death, dialysis initiation, and hospitalization among individuals with CKD. The pathophysiology is multifactorial and likely includes decreased oxygen delivery and increased reliance on anaerobic metabolism, thus generating lactic acidosis in response to exertion; the effects of chronic metabolic acidosis and hyperphosphatemia on skeletal muscle myocytes; protein-energy wasting and sarcopenia; and depression. Physical activity has been shown to improve fatigue in some small but promising trials, and so should be recommended, given the additional benefits of exercise. Targeting higher hemoglobin levels with erythropoiesis-stimulating agents may improve fatigue, but potential adverse cardiovascular effects preclude their use to solely treat fatigue without the presence of another indication. Current guidelines recommend cautious individualization of hemoglobin targets for those at low cardiovascular risk who still experience fatigue or functional limitation despite a hemoglobin level of 10 g/dl. Sodium bicarbonate supplementation for the treatment of metabolic acidosis may also improve functional status. Selective serotonin reuptake inhibitors have not been consistently shown to improve fatigue in patients with kidney disease, but an ongoing trial will evaluate the effect of alternative antidepressant drug and behavioral activation therapy on fatigue in patients with CKD. Overall, more research is needed to further clarify underlying mechanisms of fatigue and identify effective, targeted treatments for patients with CKD.

Early experiences of rehabilitation for patients post-COVID to improve fatigue, breathlessness exercise capacity and cognition

Patients with lasting symptoms of COVID-19 should be offered a comprehensive recovery programme. Patients that completed a six week, twice supervised adapted pulmonary rehabilitation programme demonstrated statistically significant improvements in exercise capacity, respiratory symptoms, fatigue and cognition. Participants improved by 112m on the Incremental Shuttle Walking Test and 544 seconds on the Endurance Shuttle Walking Test. There were no serious adverse events recorded, and there were no dropouts related to symptom worsening. COVID-19 rehabilitation appears feasible and significantly improves clinical outcomes.

Three-Day Dietary Manipulation in Multiple Sclerosis: Exercise and Fatigue Outcomes

Background: In persons with multiple sclerosis (MS), the effect of nutrition on exercise performance and fatigue remains unknown. The objective was to determine whether a 3-day diet high in triglycerides (FAT) compared with a 3-day diet high in carbohydrates (CARB) would improve fatigue and exercise performance in persons with MS. Methods: A randomized controlled crossover design was incorporated to study FAT versus CARB on submaximal cycling endurance (60% of peak oxygen consumption), substrate utilization, and fatigue in 12 persons with mild-to-moderate MS (Expanded Disability Status Scale score, 2.0–5.0) and 12 age- and sex-matched controls. Results: There were no differences in cycling time between diets in either group (P = .29). The MS group had no changes in fatigue between diets (P = .64); the control group demonstrated increased total mental fatigue after FAT (P = .05). The control group increased carbohydrate oxidation by 24% at rest and 13% during exercise after CARB. Similarly, the control group significantly increased fat oxidation after FAT by 22% at rest and 68% during exercise (P = .01). These changes were not seen in the MS group. Compared with controls, persons with MS oxidized approximately 50% less fat during exercise after FAT (P = .05). Conclusions: Neither CARB nor FAT altered submaximal exercise performance or baseline fatigue in the MS group. The results suggest that persons with MS are unable to adapt to dietary changes and oxidize fatty acids as efficiently as controls.